February Revolution in Russia.

Following defeats on the Eastern front, Tsar Nicholas is forced to abdicate. The Russian Republic is born.

Following the outbreak of the war, Tsar Nicholas began acting as a commander-in-chief of the Russian army. This proved to be a disastrous idea. Lacking significant military skills, and commanding an army that was outdated and badly organized, he suffered numerous military defeats. What's more, it left the capital in the hands of his wife and Rasputin.   This weakened his authority and led to the mass riots that forced Tsar Nicholas to abdicate in hope to save the throne for his son. This did not work, and the Russian Empire was replaced with the Republic of Russia under the feeble command of the Provisional Government.   The war against the German Empire continued, but the Russian Republic was at least temporarily forced to remain on the defensive, suffering some territorial loses in the transition period.